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Diesel vs. Hybrid: A Point Missed

VW's already developing diesel hybrids. They see it as less important because their regular TDi's already get similar gas mileage to hybrids anyway, and their super mileage TDi's (the Polo and Lupo) get Insight-type gas mileage from a 4-seater, again with no need for hybrid tech.

CO2 is produced in accordance with how much fuel you consume. If you're getting 50mpg with a diesel, you're still only putting out 50% as much CO2 as a gasoline car getting 25mpg, and the same as a hybrid getting 50mpg on gas.

Diesels actually have a big advantage on the CO2 front because a lot of places already sell B20 (20% biodiesel) which means you'll only be putting out 80% as much net CO2. On B100 biodiesel, you're putting out zero net CO2 because it was produced as a lifecycle from plants and organisms that removed CO2 from the air. As the cost of petrolium continues to increase, you'll see more and more biodiesel and in higher concentrations, thus reducing CO2. There's no equivilent fuel substitute for gasoline cars since they can't run more than 10% ethanol without being specifically tuned to run higher concentrations.

Diesel vs. Hybrid: A Point Missed

I don't buy this whole "biodiesel produces 0 net CO2 because the plants absorb CO2 before they are processed into fuel" thing.

First of all, the processing of the plants into CO2 probably uses some kind of fuel up the line. Unless the processing plant is 100% solar, wind, or nuclear powered, that processing plant is producing a LOT of CO2 somehow.

Second of all, we're not comparing the fuel manufacturing processes. We're comparing fuels.

Third of all, the comparison is not about what FUTURE TECHNOLOGIES will yield as far as CO2 is concerned. Such as it is, you can't even compare a 100% biodiesel car to a hybrid in terms of CO2 emissions because biodiesel technology is a FUTURE evolution of what petrol-based diesel is today. If you REALLY want to compare apples to apples, compare CO2 emissions from a biodiesel engine to a fuel-cell engine (the next logical descendant of hybrid technology).

And lastly, since we're comparing apples to apples, instead of speaking in terms of percentages, let's see some real quantities of CO2 spewed out by TODAY'S diesel engines vs. TODAY'S hybrid engines. And let's see some real numbers on emissions from TOMORROW'S 100% biodiesel engines and TOMORROW'S fuel-cell engines.

Diesel vs. Hybrid: A Point Missed

And yes, fuel-cell technology is VERY MUCH relevant. Fuel-cell technology is THE VERY REASON that GM has decided not to go headstrong into hybrid technology; they decided that fuel-cell research was a much better investment in the long run. Sucks that they're missing the boat, but in all honesty, I see their point.

Fuel-cells are ALREADY capable of powering cars, buses, what have you. The only problem is the fuel infrastructure. Diesel technology doesn't have QUITE the problem that fuel-cell technology does, but diesel isn't exactly available everywhere. Once fuel delivery/infrastructure problems are solved, I feel that fuel-cell technology will be far superior to both hybrid technology and diesel technology.

Diesel vs. Hybrid: A Point Missed

Tim , I'm with you on that one.
Gasoline Hybrid is the best stepping stone to the next fuel source.

If one were to do a google search on 2004 Golf TDI average MPG you'd find low 40's, which is only slightly more than a Toyota Corolla, but without the poor quality issues plaguing VW. This is still about 10MPG less than the Civic Hybrid or Prius average.

The VW Polo was mentioned but not many people here would buy a 17 second from 0-60 car (Or want to be behind one)
Imagine being stuck behind a slow 7 year old smokey, worn out Lupo?

Diesel vs. Hybrid: A Point Missed

"A gallon of diesel produces about 10 percent more carbondioxide than gas does. A point not to forget when comparing different technologies."

This has to do with the higher energy content of the fuel, which is denser (6.6 lbs/gallon vs 6 lbs/gallon).

The important thing though, is that all things being equal (TDI engine for example replacing the 2.0L gas 4-cyl of approximately the same performance), the diesel will carry you about 30-40% farther on a gallon of fuel. Therefore the net CO2 emissions will be lower (comparing gas-gas here, not diesel-hybrid). And I'm being conservative: the base Jetta gas engine is rated at 7.1 liters/100 km (33 mpg) on the highway and the TDI is rated at 4.6 liters/100 km (51 mpg), a 54% improvement. So assuming the diesel fuel in this case produces 10% higher emissions per gallon, you will still reduce emissions by 40% over a gas engine.

You also have to factor in the energy consumption in the refining process to produce the fuel. Diesel requires less energy to produce than gasoline. You would need to factor this in for a gas-hybrid vs diesel comparison.

I find too many people forget to include the entire energy cycle in their calculations.

There are of course situations where a diesel makes more sense: steady-state interstate crusing is the forte of diesels. On the other hand for mostly city driving, hybrids probably do much better than a diesel. Since 95% of my driving is the former, a diesel makes far more sense, economically, for me.

Diesel vs. Hybrid: A Point Missed

Diesel vs. Hybrid: A Point Missed

Tim, why do you keep talking about "fuel cel" technology as if it doesn't take an incredible amount of electricity to produce hydrogen? The manufacture of renewable fuels like ethanol and biodiesel uses very little electricity because the overwhelming majority of the energy storage comes from letting plants and algae grow on their own.

Hydrogen can be produced from natural gas, but that's not sustainable because we're going to run out of natural gas one day, just like we'll run out of oil. The only sustainable method of producing hydrogen is with electricity. Since biofuels use very little electricity per BTU of output and hydrogen needs electricity for 100% of it's BTU of output, it's clear to see that there is much MORE of a negative environmental impact to produce hydrogen.

Diesel vs. Hybrid: A Point Missed

The Lupo/Polo is not really going to smoke like a gasser, even if its older. Diesels typically don't have a large increase in emissions like a gasoline car or truck when they get older.

I think the hybrid owners are overlooking a major factor against hybrids right now- the additional cost and the lower availability. If you want a Prius right now, there's a long waiting list and the prices are high. You also typically have to wait longer to get a car with the features you want. If you choose a diesel car, you don't really have to wait to get a car with alot of features- VW does not make stripped down cars like Toyota does. I really looked at a Prius, but I could not justify the cost or waiting times. Now, the Honda Civic Hybrid is not as bad for waiting time or cost, but some people just are not thrilled by owning a sedan (ie, useless trunk) or a Civic.

Diesel vs. Hybrid: A Point Missed

Magnulus:
"The Lupo/Polo is not really going to smoke like a gasser, even if its older. Diesels typically don't have a large increase in emissions like a gasoline car or truck when they get older"

If this is true, then why do most diesels begin to develop problems with blowing soot and/or gasses that are toxic and painful to humans after 7-10 years?
The TDI that I test drove in Jan '04 puffed even though it was new. It was also noisy and rough. I hear many diesel drivers admitting their cars puff smoke at times, especially when starting or idling.

I haven't found any comparable statistics to link to about aged diesel car funes but one only needs to observe what is happening on the roads around them.

"VW does not make stripped down cars like Toyota does. "
Prius, even at its base is not a stripped down car.
Additionally, the features are more likely to keep functioning, unlike VW which has a very poor quality track record.

"Some people just are not thrilled by owning a sedan (ie, useless trunk) or a Civic."

Where did that come from?
Civic has been one of Honda's main sellers from the 1970's up to today. Do you mean the Hybrid version? You're also mistaken as most HCH owners are thrilled with thier car.

All this talk about diesel cars being as clean or cleaner as hybrids are just false.
If I were to buy a TDI vs a Prius, the TDI would have pumped almost 22% more Co2 into the air for us to breathe, see my previous post.

Diesel vs. Hybrid: A Point Missed

American diesel fue was low cetane in the past, which means it doesn't burn as clean. Cetane is similar to octane in gasoline, but it measures the ability of the fuel to ignite under pressure. Usually it was anywhere from 37-42 cetane. A diesel car engine really requires at leas 48 cetane to run at its best. Add cetane boosters, like about 10 ounces of Diesel Kleen or Redline Diesel Catalyst to the tank and it will not produce smoke while driving. Biodiesel is also higher in cetane and burns cleaner. Some diesels in the US will produce a little smoke at startup, though, but as the engine warms up this goes away quickly (gasoline engines produce emissions at startup, but you can't see them). Starting in 2006 all diesel fuel will have higher cetane numbers and less sulfur, and it is already being phased in gradually, which is one reason why diesel prices are rising (the other is because refiners are selling diesel to Europe).

Older diesels were less efficient and usually didn't have any emission controls, that's why you see the smoke cloud sometimes. Not because they are old. I drove behind an old Volvo 240 diesel from the 80's today that didn't have any smoke.

Diesel engines do produce more noise than a gasoline engine, under certain conditions. Such as at idle. OTOH, at highway speeds they are quieter than the typical gas car because the engine is not working as hard. Newer diesels (last 2 years) using higher pressure injectors and fuel lines produce less noise.

I'll be honest, my 2003 Jetta is not as quiet as a Prius or Honda Civic Hybrid. It sounds like a bus at idle (not nearly as loud, of course) and the steering wheel transmits more vibration than the typical gasser. OTOH, I don't find it objectionable and at 35-50 mph cruising it doesn't make much noise. The engine is not the newest, though, it's a VE fuel pump, not a common rail or PD (pumpe deuse- unit injectors), which produce somewhat less noise. My car also doesn't produce any smoke at startup- you could stick a white cloth under the exhaust for a minute, pull it out, and the cloth will not have anything on it.